Drupal 7 Module Development

Creating Your First Module
Drupal supports dozens of languages. This is one of the strongest features of
Drupal's internationalization and localization effort. The method by which
Drupal supports translation is largely through the t() function.
There are three features of this function that every developer should understand:
• What happens when t() is called
• How Drupal builds the translation table
• Additional features you get by using the t() function
First, let's look at what the t() function does when it is called. If no language
support is enabled and no second argument is passed to t(), it simply returns the
string unaltered. If more languages are enabled and the user's language is something
other than English, Drupal will attempt to replace the English language string with a
string in the appropriate language.
The second thing to look at is how Drupal builds the translation information. There
are two aspects to this: The human aspect and the technical one. The translations
themselves are done by dozens and dozens of volunteers who translate not only
Drupal's core, but also many of the add-on modules. Their translations are then
made into downloadable language bundles (.po files) that you can install on
your site.
On the more technical side, this dedicated group of translators does not simply
search the source code looking for calls to the t() function. Instead, an automated
tool culls the code and identifies all of the translatable strings. This automated tool,
though, can only extract string literals. In other words, it looks for calls like this:
t('This is my string');
It cannot do anything with lines like this, though:
$variable = 'This is a string';
t($variable);
Why won't the translation system work in the case above? Because when the
automated translation system runs through the code, it does not execute the code.
It simply reads it. For that reason, it would become cumbersome (and many times
impossible) to determine what the correct value of a variable is.
The locale module can, under certain circumstances, identify
other strings that were not correctly passed into the t() function
and make them available to translators. This, however, should not
be relied upon.
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